802
FXUS63 KILX 081115
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
615 AM CDT Mon Jun 8 2026

.KEY MESSAGES...

- A Flood Watch is posted today and evening for central and
  southeast IL. A few waves of showers and thunderstorms
  expected today and could produce locally heavy rain of 2 to 3
  inches per hour rates.

- High heat and humidity will build across the region Tuesday
  through Thursday, driving afternoon heat index values into the
  upper 90s and lower 100s. More comfortable temperatures and
  humidity levels are expected by early next week.

- There is a Slight to Enhanced risk of severe storms from the
  IL river nw Wed night. There is a 15-30% risk of severe storms
  over central and southeast IL Thu and Thu evening as cold
  front moves through Thu night.

&&

.DISCUSSION...
Issued at 400 AM CDT Mon Jun 8 2026

Issued a Flood Watch for central and southeast IL today and
evening. Some bands of showers and thunderstorms to pivot north
and ne across the areas today, with best chances of convection
shifting into east central and southeast IL this evening.
Unseasonably high precipitatable water values will be 2-2.25
inches at times today and evening over the CWA. Thunderstorms
could produce locally heavy rains of 2-3 inches per hour rates
and to be more widespread than the past few days as mid level
trof moves into IL this afternoon. WPC Day1 ERO has slight risk
of excessive rainfall across CWA today/evening with southeast
IL (Terre Haute to Shelbyville south) having a 25% risk of
rainfall exceeding flash flood guidance within 25 miles of a
point.

A mid level trough over western MO/IA early this morning will
move northeastward today across the mid Mississippi Valley.
Deep tropical moisture continues streaming over IL ahead of
approaching trof with PW of 2-2.25 inches into this evening.
Weak steering flow aloft to also support heavy rain threat. Will
Moderate instability is forecast into southern Illinois this
afternoon along with enough wind shear to support marginal risk
of severe storms from mid afternoon into early evening in
southeast IL. Main severe storm threat is damaging wind gusts
while also a 2% risk of tornadoes from highway 50 south. The RAP
13 Layer Non-supercell tornado parameter has pockets of 1-3
over central IL from mid day into the afternoon. So we will need
to be alert for possibility of a few brief funnels/tornadoes in
tropical air mass. Highs today of 80-85F, warmest near
Lawrenceville with muggy dewpoints in the low to mid 70s.

Convection chances to become more widely scattered from west to
east during tonight as mid level trof shifts east into Indiana
tonight and instability wanes. Moderate to heavy rains still
possible over east central and especially southeast IL during
early to mid evening. Lows overnight in the upper 60s to around
70F.

Mid level trof continues moving east over the Ohio river valley
on Tue with upper level ridging into IL as 500 mb heights rise
to 588-590 decameters by Tue afternoon over CWA. SPC Day2 has
marginal risk of severe storms over CWA Tue afternoon/early Tue
evening as an unstable air mass lingers over the area with very
warm temperatures in upper 80s to around 90F and moist
dewpoints in the low to mid 70s. Large hail and damaging wind
gusts will exists with any storms that can become sustained in
that thermodynamic environment from mid Tue afternoon into early
Tue evening until sunset.

Mid/upper level ridge over IL on Wed and this to keep most of
area dry much of the day Wed along with hot and humid
conditions. Highs Wed in the lower 90s and dewpoints in the low
to mid 70s to give afternoon heat indices in upper 90s and lower
100s (highest over the IL/MS river valleys). Will see breezier
sw winds on Wed with gusts 20-30 mph especially Wed afternoon
due to tightening pressure gradient.

Per SPC Day3 Outlook for Wed night, they have a slight risk of
severe storms from the IL river nw and enhanced risk over nw
parts of Knox and Stark counties. (Also have a Level 1
intensity of severe nw of the IL river). Here is SPC`s
discussion on this severe threat for Day 3 (Wed afternoon/Wed
night)...A very moist boundary layer, characterized by boundary
layer dewpoints in the upper 60s to mid 70s is forecast ahead of
a cold front, which coupled with steep lapse rates, will
contribute to moderate to strong instability Wed afternoon.
Thunderstorms are expected to develop over IA and the lower MO
Valley by mid to late Wed afternoon. The strongest deep layer
shear is forecast across the upper MS Valley into upper Midwest,
with decreasing bulk shear magnitudes with southward extent
being offset by stronger instability. The CAPE/shear parameter
space will favor organized storm modes including supercells and
bowing structures. Large to very large hail will likely be the
initial hazard, with the threat for damaging winds and tornadoes
increasing as storms move into northwest IL, where stronger low
level shear is forecast.

SPC Day4 Outlook has 15-30% risk of severe storms over CWA on
Thu especially Thu aftn/evening. The highest risk is from
Champaign to Litchfield northwest. We will likely be in a
severe risk on Thursday (especially Thu afternoon/evening) as
line of storms pushes se over central and southeast IL into a
very unstable air mass with stronger wind shear present due to
50-70 kt mid level jet streak. Per SPC Day4 discussion...There
is some model signal that a corridor of enhanced tornado
potential could develop along and south of the surface low track
from eastern IA and northern IL. That potential scenario will
be dictated by the location of the effective surface
boundary. High heat and humidity ahead of the storms especially
se half of CWA where highs around 90F to lower 90s and
afternoon heat indices peaking in the upper 90s to near 100F
before the storms move in. Precipitatable water values remain
high on Thu so heavy rains are a threat especially if training
occurs. WPC Day5 ERO has marginal risk of excessive rainfall
across IL on Thu/Thu night.

Quieter weather expected on Friday behind the cold front with
just slight chance of convection southeast of I-70 Fri morning,
with better chances of convection shifting se of CWA. The ECMWF,
GEM and GFS models keep much of area dry Fri through Saturday
though NBM and WPC have 20-40% pops Fri night and Saturday.
Still fairly warm Fri/Sat with highs in the mid to upper 80s and
a bit sticky with dewpoints in the 60s both days. Another cold
front to push into central/se IL around Sunday and to bring a
chance of showers and thunderstorms Sat night and Sunday,
followed by cooler and less humid air early next week (highs
upper 70s/lower 80s Sun/Mon June 14-15).

The Climate Prediction Center (CPC) 8-14 Day outlook for June
15-21st has a 35-45% chance of below normal temperatures over IL
with 35-40% chance of above normal precipitation.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 612 AM CDT Mon Jun 8 2026

MVFR ceilings are quickly spreading northeast early this
morning, and should stick around until about 18z or so. Timing
of thunderstorms remains challenging, but the main threat should
be from mid morning through late afternoon. Showers will
diminish by early evening, but as a low pressure area passes by
eastern Illinois, ceilings will lower back below 2000 feet from
KBMI-KCMI by late evening.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for ILZ027>031-036>038-
040>057-061>063-066>068-071>073.

&&

$$

KEY MESSAGES...07
DISCUSSION...07
AVIATION...Geelhart